A Par (Parabolic Aluminum Reflector) lamp for indoor illumination is a projecting lamp. A Metal Halogen Lamp is an LED Par lamp has tens or more than one hundred watts to generally function as the light source for the conventional Par lamp and only requires an array-chip LED of several or more than ten watts. A regular shadow occurs if a lens with smooth surfaces is used in multi-chip LEDs because the arrangement of the chips one by one produces an imaging effect in the light spot projected. With regard to LEDs having chips with different colors including red, green and blue, uneven light spots with colors may present at different locations in the projection area. In this case, a light mixing process is generally required. Referring to FIG. 2, the basic structure of most of the current lens comprises a smooth aspheric lens in the centre, around which a circular arrangement of total reflection prisms are located. Such lens has a very large height as the lamp has a relatively large caliber which requires the use of a much thicker plastic material when injection molding. This causes relatively strong shrinkage, and also a relatively long cycle time needed for injection molding of a single lens. Consequently, this influences the light distribution performance, production efficiency and cost of the lens.
There is a desire to produce a secondary optical lens with a height that is reduced to half of that of the prior art lens. There is also a desire that this secondary optical lens has reflective surfaces to reflect light and enable light mixing such that the projected light spots change gently and the light spot has the same color temperature in the centre and at the edge. This eliminates the shadow caused by the arrangement of LED chips presented in the projected light spot due to imaging effect.